Casting machine



May 29, 1923.

J. A. M MANUS CASTING MACHINE Filed Oct. 11 1919 DIME Mil my fm/emiox;23 a4r4mm,

Patented May 29, 1923,

JOHN A. MCMANUS, OF LYNN, MASSACHUSETTS.

CASTING MACHINE.

Application filed. October 11, 1919. Serial No. 330,151.

To all whom it may concern:

Be it known that I, JOHN A. MOMANUS, a citizen of the United States,residing at L nn, in the county of Essex and State of M assachusetts,have invented certam new and useful Improvements in Casting Machines, ofwhich the following is a specification.

The present invention relates to casting machines of the electrical typeand embodies certain improvements, both mechanical and electrical, overthe construction shown in my previous inventions, the subjects ofPatents Nos. 1,015,818 and 1,015,819, respectively, both of whichpatents were issued January 30, 1912.

While the machine illustrated in this application and those illustratedin my former patents have been designed more w1th a view to. theirutilization in connection with the making of dental castings, such asfor inlays, crowns, bridges, porcelain work, etc, the same principle,with slight modifications in the structure of the apparatus, may beequally as well applied to the cast ng of jewelry, such as gold rings,small trinkets, etc., where metal or other diesor moulds may be used tobe filled by centrifugal casting methods, and, of course, if largerscale operations are desired, suitable modifications in design willreadily adapt the apparatus to such purposes.

The machine of the present invention is more particularly an improvementover the previous design illustrated in my Patent No. 1,015,818, in thatin the resistance furnace type of centrifugal casting machine I havesucceeded in producing a machine which is adaptable to both alternatingand direct current supply circuits; and which at the same time is lightin weight and more simple in operation. In the machine shown in PatentNo. 1,015,818, an alternating current transformer was necessary tofurnish current to the crucible or furnace at about 4 or 5 volts andabout 100 amperes. The machine was limiteddn its application toalternating current circuits only. A motor was also employed to lo tatethe machine. The whole equipment, therefore, machine, transformer, andmotor was relatively heavy. In the present improvement I have succeededin making a machine which is not only adaptable to both alternating ordirect current supply circuits, but one which eliminates the need of atransformer or other current changing device and also of a motor, andis, therefore, light in weight and simple in its construct on andoperation, the whole outfit Weighing approximately only 9% pounds, as

machine. One of the essential factors contributing to the success ofsuch a machine is the emplo ment of a crucible or furnace having suitaical other special applications, and which is adaptable to being heatedwithout the necessity for using an unduly heavy current or large energyinput in proportion to the Work to be performed. While the carboncrucible of my previous patents has the other desirable properties itrequires to be run at a high current density. I, therefore, after anumber of years of patient research and failures in the enduringqualities of the furnace heatin means, have succeeded in producing acrucible of such material and proportions of wlnding as to successfullyfulfill the ob- JGCtS to be attained. A successful crucible or furnaceelement was finally made by using a crucible of alundum suitably groovedaround the sides and bottom for the reception of a winding in the natureof a platinum coil wound into a helix. This helix is formed by windingthe platinum wire on a mandrel of suitable size and then stretching thecoil thus formed to avoid any possibilities of short circuiting betweenadjacent turns of the helix. The helix is then wound into the grooves,covered in by alundum cement and allowed to harden and graduallysintered by slow heating with the electric current passed through thehelix up to the working temperature. Many adjustments as to length ofhelix, section of platinum wire, and distribution of the wire around theworking portion of the crucible had to be made befor the properrelations could be established and a crucible produced which would havea long life. In fact, the experiments involved covered a period ofseveral years of construction and testing, before long lived crucibleswere obtained, which would ive eflicient results with the leastexpenditure of money, when dealing with such an expensive resistancewire as platinum, or the like.

Another object of the invention, also, 15 to provide a resistance typeof furnace, wherein the furnace itself is mounted on the, central axisof rotation, thus enablingthe machine to be made of minimum dimensions,and at the same time to allow a high speed of rotation to be quicklyattained. This can be done very readily by means of a suitable handdrive, such as by a gear and pinion, by means of releasing a coiledspring, or any other suitable means. This central disposition of thecrucible also has the advantage that the metal or material whichis fusedtherein will not leave the crucible to enter the mould until asufiicient force the rotation of the crucible to cause the moltenmaterial to be forced into the mould under an appreciable pressure,which in turn produces a sound homogeneous casting, after the latter hascooled; free from blow holes,

etc.

By the use of a crucible wound with conducting wire of relatively highresistance,

'such as platinum,

pensive,

for example, I am able to produce the necessary heating effect of thecurrent to fuse the desired metals to be cast, and at the same timeeliminate the use of a transformer or alternating current circuits, orto dispense with other current changing devices where direct current isemployed. While platinum is at present somewhat exthe amount used forthe particular Work to which the machine is applied is not prohibitive;and the elimination of a transformer or other special devices, and theease and facility of operation of my improved machine, warrant its use.Also. for-lower temperature work, where gold or silver is not employedas the casting material, resistance wire of cheaper grade may be usedwith which to wind the crucible, such as nichrome, or caloriteresistance wire.

For certain high temperature applications,

such as for the reduction of high fusing.

porcelain in the furnace, it may be desirable to use a resistor having ahigher melting point than platinum and in such case means for heatingthe mould may also be desirable. I have shown a modificationin theaccompanving drawing employing such means.

- While I have in the present embodiment of my invention elected to usecentrifugal force to transfer the fused material from the furnace intothe mould, I do not limit no self entirely to dependence u n centrifugalmeans-to make this trans er. The same result could be'accomplished, forexample, by shocking the'molten material into the mould, such as byreleasing a spring attached to the furnace in a manner to dishas beendeveloped by flask and mould, or by using my e ectrically heatedcrucible or muflie in conjunction with a vacuum machine and sucking thecasting material into the mould after it has been fused. Y

In the specific form of my invention, as adopted by me, I have usedcrucibles of alundum, but zircite, quartz, or any other refractorymaterial, suitably shaped and wound, may be used, provided it meets therequirement of chemical inertness where such property is desirable.

Still another object of my invention is to combine in my improvedcasting machine an electrical heating means for melting or evaporatingout the disappearing wax model invested in the casting flask.

In the application of my machine to the casting of dental inlays,particularly, I have found that the melting out of the so-calleddisappearing wax model electrically gives far better results than anyother method heretofore used. Ordinarily, this model or pattern ismelted out by putting the flask containing the same into or over a gasflame and endeavoring to regulate the amount of heat and the timeconsumed in the process by adjusting the gas flame. In the meltingloutof these wax models it is very essential t at the result be accomplishedslowly and evenly, in order that the contour or margins may not bebroken down, but may be retained sharp, clean-cut, and true to the oriinal. This result is very difiicult to accomp ish by ordinary gas flameheating. It is quite obvious that with an electrically heated baking cupthe winding can be properly proportioned, or the control of the heatingbe almost perfect by means of a rheostat or taps taken from thewinding.Thus the wax model or pattern may be gradually absorbed by theinvestment material, or evaporated.

The specific embodiment of the desirable features of my improvedelectrical casting machine will be more clearly illustrated by referenceto the accompanying specification and drawings, in which Fig. 1represents a side elevation of my improved casting machine with thefurnace .cover partly broken away and the hollow supporting posts brokenaway to show the method ofwiring; Fig.2 represents a vertical section onthe line (Ir-(Z, Fig. 1 showing the construction of the crucible, orfurnace, and the wax dissolving device; Fig. 3 is a diagram of theelectrical connections; and Fig. 4 a modification showing the heating ofboth the crucible and mould.

Referring more in detail to the drawings.

1 and 2 represent suitable plates of thin sheet posts 3 extending intoholes in the plates. The posts 3 are tapped to receive filister headscrew-threaded feet 4, or if desired these feet may be made ofinsulating material. The posts are secured at the top plate by means ofthe screws 5. Supported in the bearing block 6 is a shaft 7 which shaftextends through the plate 2, and is suitably secured at the top to aflat disk or plate 8 by means of a screw 9 and lock washer, or by anyother obvious means to secure the shaft and disk against relativemovement. Mounted on the shaft 7 is a block of insulating material 10,which may be made of some suitable wood, such as maple, or better still,of the wellknown electrical insulator bakelite. Moulded into theinsulator block 10 are two collector rings of relatively thin copper orbrass 11 and 12 The collector rings may be given a coat of silverplating, in order to prevent corrosion and poor contact. If thecollector rings ll'and 12 are not moulded into the insulating block 10,or rather, if the insulating block '10- is not moulded about them, theymay be made jointed, provided a good silver-soldered joint is obtained.Suitably mounted on the lower partof the shaft 7 is a small pinion 13spaced from the bearing block by a thrust Washer (not shown). eshingwith the pinion 13 on the under side of the plate 2 is a large ear 14having a ratio of about 10 :1 in relation to the pinion. This gear issupported by means of the shaft 15 and hub 16, the shaft 15 extendingthrough a hole in the plate 2 and secured at the top of the plate by anut 17 and lock washer 18. Secured to the gear 14 by screws 19 and 20,or other suitable means, is a handle 21 for turning the gear by hand andconsequently enabling the furnace or crucible element to be rotated at afairly high speed. While I have used a gear drive, of course, anysuitable driving means may be used, such as a wound-up clockspringattached to the shaft 7. Also mounted on the plate 2 are two brushholder studs, one of which is shown at 22,whic'h carry thin copper orbronze brushes for engaging the collector rings 11 and 12. 24 representsa furnace or crucible container which may be made of a spinning of thinsheet metal, such as sheet steel. and made in the form of a cup having aclosed bottom and open top. This cup may be secured to the disk or plate8 by means of the same screw 9 which secures the shaft 7 to the disk8,or the cup and disk may be made in one piece, as desired. A cradle 25of insulating material, such as bakelite or asbestos board is laid onthe bottom of the cup 24 and serves as a support for the crucible 26,the latter being made of any suitable material which will stand thetemperatures involved. In the present instance I have made this crucibleof alundum, a trade product of the electric furnace, which ispractically pure fused alumina, and furnishecl in desired shape, uponrequest, by the manufacturers of such materials, the material beingformed and sintered at high temperatures thereby having a verynegligible expansion coefficient and subject to very little tendency tocracking. The crucible, however, may also be made of such materials aszireite, fused quartz, or other materials somewhat analogous inrefractory and chemical properties. One of the desirable characteristicsof such a crucible for dental applications is that it be chemicallyinert to silver and gold of relatively high karat quality (22 karat forexample), as it is desirable that the casting materials used do notcombine chemically with the material of which the crucible is composed,or with the platinum winding, when platinum is used as the resistancewire. Moulded or ground into the bottom of the crucible 26, and a shortdistance up the sides thereof, are suitable grooves for the reception ofa helix of high resistance wire 27. In the present instance I havechosen platinum as the wire of which to make the helix, on account ofits relatively high resistance and high melting point. This helix iswound on a suitable mandrel until a length of the required proportionshas been obtained, the section of wire also being chosen which will givelong life, without burnouts. When the helix is slid off the formingmandrel, the adjacent turns are carefully stretched to give them a setwhich will avoid short circuiting of the turns, or the helix may bewound on the mandrel by means of a spacer wire between the turns. Thehelix is then laid into the grooves formed in the crucible, and woundtherein, being secured temporarily by an elastic band, A number ofcoatings or paintings of insulating cement, such as alundum cement, isthen spread over the wire, each coat being allowed to dry before thenext one is applied, etc., until a sufiicient thickness has beenobtained. Leads 28 and 29 are then secured to the ends of this helix,which leads I choose to make about twice the section of the helixitself, in order to have a long life. This has been found by experimentto be desirable. While I also make these leads of platinum of relativelyshort length and thick section, it is conceivable that heavy leads ofcheaper material than platinum may be employed. such as heavy copperleads, for example. Electric current is then passed through the leadsand helix slowly increasing in value up to the working temperature, inorder that the insulating cement may be sintered or rendered relativelyhomogeneous with the crucible itself. Insulating bushings 30 and 31 areinserted through the cup 24 and disk 8. through which bushings the leads28 and 29 are passed and connected to thecollector rings. An insulatingdisk of mica or other suitable insulator 32 is inserted over thecollector ring block, and this efiectively prevents any possibility ofthe leads 28 and 29.

coming in contact with any metal parts as they are carried to thecollector rings. One lead such as carried through the bushing 30 underthe insulating ring 32 and silver-soldered, brazed or otherwise properlysecured to the top ring 11. The lead 29 is passed through the bushing31, under the insulating ring 32, and down through a hole in thecollector ring block to the lower collector ring 12, where it is alsoproperly secured to the latter. While the connection of the heavy leads28 and 29 is shown as being made inside the .container 24 in a temporarymanner, as by small nuts and washers, a permanent joint may be made atthe helix itself, and a temporary joint made outside, that is,underneath the container 24, where the joint will be more accessible incase a repair should be necessary. A packing of insulating material,such as asbestos wool, silicon, monoxide, or other suitable heatnon-conductor 33 surrounds the crucible 26 in the container 24, in orderto thermally insulatethe crucible and minimize loss of heat. Aninsulating cover 34, with a little knob or handle 34', is provided tolie.

over the top of the crucible for the same reason. This cover can beremoved at will to inspect the condition of the casting material in thecrucible, and determine when material becomes fused or melted. Thecrucible 26 is formed with a mouth or spout 35 and with gradual risefrom the bottom of the crucible to the spout, in order that a certainminimum effect of centrifugal force will be generated before the gold orother casting material will leave the crucible prior to entering themould 36 in the flask 37, This ensures that a certain initial force isinvolved before the casting material starts to enter the mould. Theflask 37 may be the conventional casting ring used in dental inlaycasting, that is, a cylindrical shell, open at both ends, and previouslyprepared and filled as described in my former patents above mentioned,In order to retain the casting ring or flask in place, in operativerelation with the crucible 26, a hole is provided in the cup 24, ofsuitable dimensions to receive the flask 37 and a bail wire 38 extendsaround the cup 24 and flask 37 in a manner to retain said flask fromflying out by the action of centrifugal force. The bailwire 38 istightened and loosened at will by means of an eccentrically disposed cam39, through which the wire 38 extends. This cam is operated by means ofa lever 40, which may be pushed up or pulled down in the direction ofthe arrow;

Referring to the wax dissolving device, 41 represents a thin shell ofsheet steel spun into the form of a cup, in which cup is the lead 28,for example, is

saidmounted a core of suitable insulating matenal, such as soapstone, orartificial composition held together with a binder and fused or baked atthe proper temperature.

temperatures, and 1n this case suitable for Y producing a temperaturesufficient to melt the wax model or pattern by conduction or radiationof heat into the flask '37 when the latter is inserted to rest in thecore 42. Surrounding the core 42 and helix 43 is a body of insulatingmaterial 44, which may be either a solid block-into which fits the core42, or this insulating material may be powdered or granular, packed intoplace. Assuming that it is solid, which is the preferable form, anopening 45 is cut or bored through the core 42 and block 44, largeenough so that a small screw-driver can be lnserted through the core 42from'the top and thus the cup 41 and block 42 secured to the plate 2 bymeans of the screw 46. Two insulating bushings 47 and 48 are insertedthrough the bottom of the cup 42 and holes formed in the block 44,through which the I leads 49 and 50 are taken out.

On the lower plate 1 is mounted a small rheostat comprised of the threeinsulator plates, 51, 52 and 53 between which is suitably supported acoil of high resistance wire 54, 54. Again, this coil is made ofnichrome, calorite, or any other well-known resistance 'wire which willwithstand temperatures up to a low red heat, the coil being fastened tothe insulator plates and the upper portion 54' beinghcontinuous with thelower portion 54. A hole in the plate 52 permits the coil to be strungthrough to the compartment between the plates 52 and 53.

studs 59, 60 and the two rear studs (not shown). The studs are screwedinto tapped holes in the plate 1 to receive them. A shaft 61 isjournalled in the plates 51, 52 and 53, to which shaft is attached acontact spring member or arm 62, which has a sliding contact engagementwith the upper portion ofthe coil 54. A hard rubber handle 63 issuitably fastened to the shaft 61 and this handle carries an indicatorneedle or pointer 64, in order to determine the position of the contactarm 62 and consequentl to indicate the amount of resistance whic is cutin or out of circuit. The insulated conductor of copper wire 65 isconnected to the brush-holder stud 22 and passes through the hollowsupporting post 3 to the rheostat where it is connected to one side ofthe latter in series, the other side of the conductor 65 being connectedto the opposite end of the rheostat from which it is carried through thecorresponding hollow supportin 3' to a switch 66 mounted on the switch pate 67, the latter being sup orted on the right hand supporting posts.rom the switch a connection 68 is carried to the under side of thebinding post 69 and still another connection 70 is connected to the lead49 of the wax dissolving unit carried in the cup 41. A similarconnection (not shown) is connected to the lead 50 to another point onthe switch 66. 71 and 72 represent the main supply wires connected tothe binding post 69 and its cor responding binding post in the rear (not'shown). From this latter binding post is carried a conductor, which isstrung through its corresponding hollow supporting post and through thehollow tube 73 in the rear of the machine, and from thence to the rearbrush-holder stud, the current passing through the brush, through thecollector ring andcrucible to the opposite brush to the conductor 65,through the rheostat and out through the main 71. The diagram ofconnections, F ig. 3, will illustrate moreclearly the paths of thecurrent in the respective circuits. 71 and 72 represent sup 1y mains forsupplying a source of A. C. or C. current at preferably 110 volts. 73represents a switch in the main supply circuit for entirely shutting offthe supply of current to the machine. 66 represents the switch Fig. 1mounted on the machine itself, which switch, in the present instance,controls only two circuits, one through the crucible and rheostat, andthe other through the wax dissolving unit. It is to be understood,however, that this switch may have another point giving an off position,and thus dispensing with the need for the outside switch 73.

In the diagram, 26 represents the crucible and 43 the wax heater, as inthe other figures, and 54 the regulating rheostat. 62 represents thespring contact arm on the rheostat and 11 and 12 the slip rings on thecollector. 11' and 12' represent the brushes bearing on these respectiveslip rings.

I will now describe the operation of my improved casting machine:

Assuming that the flask 37 has been prepared in the usual way and thewax pattern 36 inserted therein, this flask is then inserted in the core42 of the cup 41. The knob 66 of the switch 66 is then turned until itbrings the label wax before a window opening in the switch. Assumingthat the switch 73 is closed, the switch 66 will now be in the dottedline position in the diagram and current will flow from main 71, throughswitch 66, through the lead 49 of the wax heater, throu h the wax heatercoil 43, out through the ead 50 to the supply line 72. The flask is leftin the wax heater until the pattern is dissolved and thoroughlyevaporated, when the flask is taken out and inserted in place inoperative relation with the crucible 26. The bail wire 38 is pulled upinto position to retain it in place, as shown in Fig. 2, and the camlever 40 tightened. The snap switch 66 is now again turned until thelabel gold appears before the window. This opens the wax heater circuitand closes the crucible circuit. The switch 66 is now in the positionshown in full lines in'the diagram. The insulating cover 34 is liftedoff the cup 24 by means of the knob 34 and gold or other cold castingmaterial dropped into the crucible 26 and the cover again replaced. Thecurrent is now flowing from the main 71, through the brush 12',collector ring 12, through the crucible winding 27, through thecollector ring 11 brush 11', through the regulating resistance 54, outthrough the contact arm 62 and finally through the switch 73 and supplymain 72, thus completing the circuit. current is allowed to flow throughthis circuit until the casting material is fused or molten, which can bedetermined by occasionally removing the cover 34 and instantly replacingit to prevent loss of heat. A little praqticeenables one to determinequite readily about the length of time required inaccordance' withtheparticular setting of the rheostat for fusing the casting materials.With 22 karat gold, for this particular type of crucible and theresistance all in circuit, the average time is from two to four minutes.When the casting material has become fused or molten, the cover or hood24' is placed over the rotatable furnace and fastened to the plate 2 bymeans of lugs 74 and thumb screws 75. This prevents any-possibility ofdanger of rotating parts in case any such should become detached, whichoccurrence, however, is quite unlikely if the parts are properly made.Conditions are now favorable for casting, and the handle 21 is grippedwith the hand and a good vigorous turning of the same for from 15 to 30seconds (preferably in the direction of the arrow) will cause thecrucible 26 and flask 37 to rotate together and cause the castingmaterial in the bottom of the crucible 26 to rise up the incline in thelatter and enter the mould 36 with considerable force while in theplastic state, filling the mould under pressure and displacing airbubbles, etc. The current is now turned ofl by opening the switch 73,and when the rotor is at rest, the cover 24 is removed, the bail wire 38is released, and the hot flask 37 is withdrawn from its seat by asuitable tool and plunged in water. The finished casting is then takenout and will be found to be a sound, homo- The 10. or they calorite, asdesired..

While I have shown one specific embodiment of my device, I do not wishto be limite( thereto, but desire to cover in'the apperded claims allmodifications falling fair-l within the scope of my invention.

W'iiat I claim as new and desire to secure by Letters Patent of theUnited States is 1. In a casting machine, the combination of anelectrical resistance furnace deriving its heat by means of currentpassed through an electrical resistance wire in operative relation withsaid furnace, means for delivering electrical energy to said resistancewire, means for controlling the amount of .electrical energy supplied tosaid furnace,

and a means for transferring fused material from the furnace to the"mould under the action of centrifugal force.

2. In a centrifugal casting machine, the combination of an electricallyheated platinum wound resistance furnace or crucible mounted onsubstantially the axis of rotation of said machine, a suitable castingflask revolvable with the furnace and in cooperative relation therewith,means for delivering electrical energy to said platinum resistancefurnace, a thermal insulating packing around said furnace, and means forrevolving the furnace and flask in a manner to cause fused or moltenmaterial in the furnace to be transferred to the flask by the action ofcentrifugal force.

3. In a centrifugal casting machine, the combination of an electricallyheated platinum wound resistance furnace or crucible mounted onsubstantially the axis of rotation of said machine, a suitable castingflask revolvable with the furnace and cooperatively' related therewith,a container for the furnace or crucible, a thermal insulating packingbetween the crucible and the walls ofthe container, suitable slip ringscooperativel connected with the furnace, conductin sh?) rings, brushholders for supporting the brushes, conductors delivering suitableelecfree from blow holes, and

rushes in operative relation with said trical energy to the brushes,means for controlling the temperature of the furnace, and means fortransferring molten or fused material from the furnace to the flask bythe action of centrifugal force.

4. In a casting machine, the combination of an electrical resistancefurnace deriving its heat by means of electric current passe through aresistance .wire wound on or in operative relation 'with said furnace, amould holdin flask also in operative relation with sai furnace, meansfor. heating the mould, an opening in the furnace communicating withsaid flask, and meansfor forcibly transferring the fused or moltencasting material from the furnace through the opening into the mould.

5. In a'casting-ma'chine, the combination the investing compound to thepatterm a gate for the reception of casting material at the outerentrance to the sprue opening or passa e, and means for forcibly transferring t e fused or molten casting material from said gate through thesprue opening into the mould formed by the dissolved or evaporatedpattern material.

6. In a casting machine, the combination of an electrical resistancefurnace deriving its heat by means of electric current passed through aresistance element in operative relation with said furnace to heat thelatter to the desired temperature to melt or fuse the charge therein, acontainer for the furnace, a thermalnsulating packing between thefurnace and the walls of the container, I

a mould holding flask in operative relation with said furnace, means forheating the flask by passing electric current through a resistanceelement in cooperative relation with said flask, means formed in themouth of said flask for the reception of the casting material to befused or melted by the furnace after said flask has been charged withthe mould, a communicating passage in the flask between the castingmaterial and the mould, and means for forcibly transferring the fused ormolten material from the mouth of the flask into the mould.

In testimony whereof I have aflixed my signature.

. JOHN A. McMANUS.

